Treatment of transparent material



Patented May 7, 1929.

UNITED STATES 1,712,178 PATENT OFFICE.

CHARLES E. SWETT, OF' WEST ROXIBURY, MASSACHUSETTS, ASSIGNOR T0 UNITEDSTATES ENVELOPE GOMPANY OF SPRINGFIELD, MASSACHUSETTS, A CORPORA- TIONOF :MAINE.

No Drawing;

A which is secured a covering of glassine paper,

or other transparent or semi-transparent material.

It is known that the'degree of transparency of panel material, such asglassine paper, may be considerably increased by the treatment of asurface of the, material with a liquid having resinous, or othertransparent matter in solutiomwhich liquid upon drying forms atransparent film. But as the transparent film resulting from thistreatment is usually on the outside surface of the patch or panel Whenit is applied to the envelope, it has been found that the glare orreflection of light from thesurface of the transparent patch or panel,gives rise to objections on the part of those required to handle largenumbers of such envelopes, as for instance, in the sorting of mail.

According to my present 1nvent1on, 1t is proposed to treat transparentpanel material,

such as glassine paper, in such a manner as to both: increase itstransparency and to reduce the glare, with a net gain in bothdirections. Broadly stated, my invention consists in treating thesurface of the panel material.

which is to be outermost so as to leave it in a matt,or non-glarecondition, and in treating the surfacc'of the material which is to be1nnermost with a transparent film formingmaterial of high refractiveindex.

' In carrying out my invention, one surface of the material is treatedwith a suitable solution which'is adapted upon evaporation to leave thesurface in a matt or non-glare condition. There are quite a number ofsolutions which will accomplish this result, among 1 which may bementioned a concentrated aqueous solution of calcium chloride. The othersurface of the material is then treated with a suitable substance whichwill result in the formation of a film having the property of increasingthe transparency of the material.

Y Quite'a number of substances may be used for this purpose; forexample, tannic acid dissolved in alcohol may be applied to form thefilm, and if desired, a material of a higher refractive index, such asterpin hydrate may TREATMENT OF TRANSPARENT MATERIAL.

I Application filed August 14, 1924. Serial No. 732,120.

be added to the solution to further increase the transparent qualitiesof the film.

The result of the above described treatment of opposite surfaces of thematerial is a decrease of the transparency of the original material dueto the glare reduction on one surface and an increase of thetransparency of the original material, due to. the formation of atransparent film on the other surface thereof. In the practice of myinvention, the

treatment for glare reduction is carried out to such an extent as todiminish .the transparency of the original material by about 25%, whilethe treatment to increase the transparency'is carried out to such anextent as to increase the transparency of the original materialabout.50%, although it is obvious that other degrees of treatment may beemployed. Considering the above figures as a concrete example, itfollows that the carrylng out of my invention results in a net gain intransparency of about 25% and a reduction of glare as measured bystandard instruments of about 50%.

. "From the foregoing it is apparent that by treating a transparentmaterial such as glassine paper, in accordance with my invention, thereis produced a material which can be used mosteffectively for the patchesor panels of window envelopes, by reason of the fact that the surfacewhich is outermost is substantially glareless, Whereas the treatedmaterial itself has a transparency greater than that of the originaluntreated material. In carrying out my invention I am in noway limitedto the use of any specific substances for treating the surfaces of thematerial, my invention of transparency resulting from the second namedtreatment more than overcoming the loss of transparency resulting fromthe first named treatment, whereby there is a net gain in thetransparent properties of the treated paper.

3. The improvement in the treatment of 5 flexible transparent materialused for the patches or panels of windowenvelopes which consists intreating one surface of said material to reduce glare, and treating theother surface of said material to increase its trans- 10 pare'ncy.

' 4. The improvement in the treatment of flexible transparent materialused for patches or panels of window envelopes which eon sists intreating one surface of said material to bring it to a matt or non-glarecondition, and treating the other surface of said material to form afilm of higher refractive index than the untreated material.

CHARLES E. SWETT.

